Hard disk drives are commonly used as storage devices for storing and retrieving digital information. For example, some of the consumer products available in the current electronics market (e.g., portable music players and cellular phones) include internal hard disk drives each with a particular storage capacity designed to accommodate user data and functions. The digital information is usually read from or recorded onto a circular disk of a hard disk drive while rotating the disk about a spindle by a spindle motor. As the disk is spun at a particular rate, the servo mechanism of the hard disk drive moves across the disk surface and is positioned over a specific track to read out information recorded on the disk.
When power is initially applied to an electronic device supplied with a hard disk drive, the hard disk drive undergoes a “spin-up” process to bring the disk up to operating speed and to initialize a startup procedure. To conserve energy and improve power efficiency, the hard drive disk normally shuts down after detecting a period of non-use. At the next disk access, the spindle motor of the hard disk drive than spins up again and re-initializes the startup procedure.
Thus, the access time for retrieving and recording data from the hard disk drive can depend on how quickly the spin-up process can be completed by driving the spindle motor to a steady-state operating speed.